Definition of ex post facto in English:

ex post facto

Pronunciation /ˌeks pōst ˈfaktō/ /ˌɛks poʊst ˈfæktoʊ/

adjective

  • Having retroactive effect or force.

    • ‘ex post facto laws’
    backdated, retroactive, ex post facto, backward-looking

adverb

  • Retroactively.

    • ‘the law is being applied ex post facto’

Origin

Erroneous division of Latin ex postfacto ‘in the light of subsequent events’.